As an example of optical coherence tomography (OCT), there has been known a swept source-OCT (SS-OCT) using a wavelength swept optical source. The SS-OCT temporally changes an emission wavelength using the wavelength swept optical source and detects by an optical detector a spectrum including a reflected light from an examination object and a reference light. A spectral signal output from the optical detector is converted into depth information by Fourier analysis.
Incidentally, since a wavelength (wavenumber) change by the wavelength swept optical source does not necessarily occur in proportion to time, there is a possibility that the wavenumber (k) and a depth (Z) may not have a proportional relationship in Fourier transform processing. As a result, an OCT signal which includes a depth profile deviated from a true depth profile may be obtained.
As a solution to this problem, an interferometer is separately provided in addition to the OCT interference optical system, and mapping data on a wavenumber is generated (see Non-Patent Document 1: “Ultra high-speed swept source-OCT imaging of the anterior segment of human eye at 200 kHz with adjustable imaging range”, Michalina Gora, Optics Express, Vol. 17, No. 17). In a spectrum domain OCT (SD-OCT), a gold mirror placed on a measurement optical path is imaged multiple times, and mapping data on a wavenumber is generated using the signals (see Non-Patent Document 2: “Full-range, high-speed, high-resolution 1-μm spectral-domain optical coherence tomography using BM-scan for volumetric imaging of the human posterior eye”, Shuichi Makita, Optics Express, Vol. 16, No. 12).
However, in the method of Non-Patent Document 1, the separate interferometer is needed. Further, even though data generated by using the gold mirror as in Non-Patent Document 2 is used, it is necessary to acquire data at a different measurement time from the original measurement time. Therefore, it is not possible to cope with an influence of temporal fluctuation in the original measurement.